I'm planning to build a toy where the kids have to connect one row of plugs to another row of plugs in the correct order using short patch cables. (A colored led on each side will let them know which ones to connect together)
My plan is to send different pwm signals out of the first row and connect the second row to analog inputs, so I'll know which output is connected to which input.
Now my question is: what happens when the kids connect an output to an output or an input to an input? Is it safe? Well the arduino nano / uno / mega (or whatever I end up using) be damaged?